The present invention relates to a microwave irradiation apparatus for irradiating microwave to an object.
A hot air type heating furnace and hot wire type heating furnace which have been used conventionally do not have satisfactory heat conduction to an object to be heated, and the heat being arrived at an outer surface of the object requires a lot of time to conduct to the inside. Accordingly, the furnaces are generally impossible to perform high energy efficiency.
Then, microwave electric power application has been studied and now the object to be irradiated can be heated quickly and efficiently by transferring the energy of the microwave directly to the object. A microwave oven is one of the typical examples of the microwave electric power application, and it is widely used for foods heating, cooking, and defrosting and the like.
Heating various foods, woods, or the like by the microwave has been known in the industrial field. In recent years, application of the microwave electric power is spreading in the plasma field, such as applying to plasma generation, etching and ashing by the microwave in a semiconductor fabrication equipment, irradiating the microwave to a gas in a quartz valve to excite a gas molecule to produce powerful UV luminescence, and applying to an ultraviolet curing type paint, adhesion materials, and printing (plate making), and so on.
Furthermore, many effects promoting a chemical reaction remarkably by the microwave irradiation are reported in the chemistry industrial field, and the microwave electric power application is also spreading to the chemistry field.
Generally, when microwave is irradiated to the object, the energy loss P due to the object is classified into a item showing a part of the energy loss resulting from the electric field E of the microwave and other item showing a part of the energy loss resulting from the magnetic field H of the microwave, and may be expressed with the following formula (I).P=(½)s|E|2+pfe0er″|E|2+pfμ0μr″|H|2  (1)
The microwave electric power application mentioned above such as the microwave oven or the like mainly tends to heat the object to be irradiated using loss by the electric field of the microwave. Moreover, the microwave electric power application relating to the above mentioned plasma generation uses the excitation phenomenon by the electric field of the microwave. Thus, the microwave irradiation system mainly uses the electric field of the microwave conventionally, for example, Japanese laid open patent publication No. 2005-44519.
Moreover, a standing wave is formed in an antenna cavity and a paper titled to “a microwave sintering equipment of a nuclear fuel” is well-known, in which the standing wave is taken out through a slit to a resonator cavity enclosing nuclear fuels, for example, as shown in a Japanese laid open patent publication No. 2002-504668.
According to the electromagnetic mode of the irradiated microwave, the microwave irradiation systems will be classified roughly into a single mode and a multi-mode. Typically, the single mode system puts an object to be irradiated within a microwave guide, and realizes by making the microwave propagate within the microwave guide.
Usually, it is so designed that only a specific electromagnetic field mode inside of the microwave guide may be propagated, the system may use selectively the strong part of the electric field and magnetic field according to the distribution in the electromagnetic field mode.
On the other hand, the multi-mode system is represented by the microwave oven such as a microwave heat furnace disclosed in the Japanese laid open patent publication No. 2005-44519 and generates many electromagnetic modes inside of the heating case where the object to be irradiated is placed. The system, however, intermingles both of the electric field and magnetic field changeable in time delicately and accordingly, and even if trying to perform mainly the irradiation of the electric field (or magnetic field) to the object, an unnecessary magnetic field or electric field is always irradiated. As a result, it is substantially impossible to control the electric field and magnetic field independently.
Moreover the equipment disclosed in the Japanese laid open patent publication No. 2002-504668 forms distribution of the electromagnetic field intensity in a resonator cavity by a slit. However, it is also substantially impossible to control the electric field and magnetic field independently.